Smart cards in security-relevant applications can be subjected to attacks in which an attacker attempts, in an unauthorized manner, to read or alter information stored on the card. In order to repel an attack, smart cards can be provided with a series of electronic protection systems which identify such an attack and switch the card into a so-called power-down operation mode. In power-down operation, the provision of the operating voltage is interrupted, such that the operation of the smart card is terminated and the attack is repelled.
When the smart card is operated again after such a termination of operation, it is possible to signal that an attack took place, in order, if appropriate, to provide measures against further attacks. For signaling purposes, the information that an attack took place is provided in a nonvolatile memory element.
When storing such an item of information for the nonvolatile memory elements, well-defined voltage and timing conditions which permit a process of writing to the nonvolatile memory by the methods on which the smart card is usually based are possibly no longer ensured on the smart card in the case where an attack was identified and power-down operation was initiated.